Spectra extraction for wavelength-modulation spectroscopy of intra-cavity absorption gas sensor

Wennian Han; Yan Wang; Kun Liu; Dagong Jia; Tiegen Liu

doi:10.1117/12.870277

9 November 2010 Spectra extraction for wavelength-modulation spectroscopy of intra-cavity absorption gas sensor

Wennian Han, Yan Wang, Kun Liu, Dagong Jia, Tiegen Liu

Proceedings Volume 7853, Advanced Sensor Systems and Applications IV; 78532X (2010) https://doi.org/10.1117/12.870277
Event: Photonics Asia 2010, 2010, Beijing, China

Abstract

Low-frequency wavelength modulation is introduced to increase sensitivity of intra-cavity absorption gas sensor (ICAGS) system. ICAGS system including erbium-doped fiber amplifier (EDFA), pump laser, tunable fiber Fabry-Perot (F-P) optical filter and gas cell is set up. Using virtual instrument technique, modulation function is generated by LabVIEW software and outputted through the AO ports of data acquisition card to tune the driving voltage of optical filter. The AI ports collect the laser power signals in a synchronous mode. Harmonic spectra can be computed by adopting the method of the Discrete Fourier Transform (DFT). According to the characteristics of different order harmonic, even harmonics and odd harmonics are analyzed respectively. Here, second harmonic is used to determine the spectral intensity, and third harmonic is mainly used to locate the position of spectral lines. With optimum 10 Hz frequency modulation, acetylene absorption experiments were carried out. The pump current of EDFA is 60 mA and the acetylene concentration in the gas cell is 1%. After spectra extraction, in the 1526 nm to 1537 nm wavelength range, 17 absorption lines of acetylene were achieved. The results indicated that the error of wavelength position is less than 0.1 nm and the minimum detection limit of acetylene is about 120x10^-6. It is possible to realize the recognition of measured gas type and multi-component gas detection for ICAGS system.

Citation Download Citation

Wennian Han, Yan Wang, Kun Liu, Dagong Jia, and Tiegen Liu "Spectra extraction for wavelength-modulation spectroscopy of intra-cavity absorption gas sensor", Proc. SPIE 7853, Advanced Sensor Systems and Applications IV, 78532X (9 November 2010); https://doi.org/10.1117/12.870277

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KEYWORDS

Absorption

Modulation

Signal to noise ratio

Fiber lasers

Absorption spectroscopy

Optical amplifiers

Optical filters

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